1. Field of the Invention
The present invention relates to a roll printing device for depositing an orientation film of a liquid crystal display device, and more particularly, to a roll printing device, which is applied to a large-sized substrate.
2. Discussion of the Related Art
Among various ultra-thin flat type display devices, which include a display screen having a thickness of no more than several centimeters, liquid crystal display (LCD) devices are widely used for notebook computers, monitors, aircraft, etc. because they have advantages such as low power consumption and portability.
A typical liquid crystal display device includes upper and lower substrates separated by a designated interval and opposite to each other, with a liquid crystal layer interposed between the upper and lower substrates. The orientation of the liquid crystal layer is controlled by the presence or absence of a voltage applied between the upper and lower substrate. Because of an anisotropic property of the liquid crystal, light transmittance through the liquid crystal changes with changes in the orientation of the liquid crystal layer, allowing the liquid crystal display device to produce an image.
When the orientation of the liquid crystal layer is not uniform, it is difficult to obtain the desired image. Accordingly, an orientation film for uniformly maintaining initial orientation state of the liquid crystal layer is formed on the upper and lower substrates.
The orientation direction of the orientation film may be established using a rubbing method or a light irradiating method.
In the rubbing method, a thin orientation film is deposited on a substrate, and a rubbing roll onto which a rubbing cloth is wound is rolled on the orientation film, thereby orienting the orientation film in a designated direction.
In the light irradiating method, a thin orientation film is deposited on a substrate, and ultraviolet rays, such as polarized rays or non-polarized rays, are irradiated onto the orientation film. A reaction resulting from the irradiation orients the orientation film in a designated direction.
When using either the rubbing or the light irradiating method, an orientation film having a small thickness is uniformly deposited on a substrate. A related art roll printing method is used to deposit the orientation film.
Hereinafter, with reference to the accompanying drawings, a roll printing method according to a related art will be described.
FIG. 1 is a schematic sectional view illustrating a method for depositing an orientation film using a related art roll printing device.
Before describing the process for depositing the orientation film using the roll printing device is described, the structure of the roll printing device of the related art will be described.
As shown in FIG. 1, a roll printing device of the related art includes a roll printing unit 1 and a substrate stage unit 3.
The roll printing unit 1 includes a dispenser 14, a doctor roll 16, an anilox roll 18, and a printing roll 20.
The doctor roll 16 engages the anilox roll 18, and the anilox roll 18 engages the printing roll 20.
A printing mask 22 having a shape corresponding to the deposition pattern of a desired orientation material 15 is attached to the printing roll 20.
The substrate stage unit 3 includes a substrate stage 12, and a substrate 10 mounted on the substrate stage 12.
Hereinafter, a method for depositing or forming an orientation film using the above roll printing device is described. First, the dispenser 14 supplies or dispenses the orientation material 15 to the anilox roll 18. The orientation material 15 supplied to the anilox roll 18 is uniformly spread by the doctor roll 16 engaged with the anilox roll 18, and is then deposited onto the printing mask 22 attached to the printing roll 20. The above process is performed by respectively rotating the doctor roll 16, the anilox roll 18, and the printing roll 20 in directions indicated by respective arrows.
The substrate stage 12, on which the substrate 10 is mounted, moves in a direction indicated by an arrow under the printing roll 20. While the substrate stage 12 moves, the substrate 10 mounted on the substrate stage 12 and the printing mask 22 attached to the printing roll 20 contact each other and the orientation material 15 deposited onto the printing mask 22 forming a thin film of orientation material 15 on the printing mask. As the printing mask 22 rotates in contact with the substrate 10, the thin film of orientation material 15 on the printing mask 22 is transcribed onto the substrate 10.
In the above-described roll printing device of the related art, the roll printing unit 1 is fixed and the substrate stage unit 3 moves, thus allowing the orientation material 15 to be deposited on the substrate 10.
However, when forming an orientation layer on a large sized substrate, the movement of the substrate stage unit 3 during forming the orientation layer is increased, thereby increasing the space occupied by the roll printing device, and lowering space utilization.